Hi Sarah - sorry you have to go through this - it must be especially scary and difficult having to understand complicated medical information presented in a foreign language. I don't have experience with SAA but I do have plenty of experience with prednisone. How much are you taking? Your post mentioned 1/2 but I don't understand what that means - 1/2 what? Prednisone can cause all sorts of ups and down - high doses (50mg per day)made it difficult for me to sleep, made me jittery and agitated - short tempered - anxious - and ravenously hungry -also reduced muscle and made me diabetic. I'm down to 15mg/2.5 mg every other day and the effects are far less pronounced.
My guess, from some internet research, is the VSG is the "velocidad de sedimentation globular" - which is the same thing as the erythrocyte sedimentation rate (ESR) or Sed Rate - which roughly speaking, measures inflammation in the body - which may be associated with a variety of conditions including autoimmune - here is a link describing the test - it sounds like your results are not abnormal - but please don't rely on me - ask your doctor for clarification - I am not a doctor and don't speak all that much Spanish -
http://www.healthline.com/health/esr#NormalResults6
Hope that helps a bit - best wishes,
Paul